A7750 - Chrono reset fails

[Mike1718]

I have bought an IWC 3717 with an A7750 movement. The watch works OK since a week (+1-2 min/day though).

I have tried the chrono and it works OK, starting and stopping. But at some occasions the reset does not work. The first time it happened after 10 tries, then it happen a week later.

Either it does not reset at all, sometimes it resets half the back to twelve, and sometimes it stops anywhere else (ie passes 12 and stops at eight o'clock,..). The subdials also fails to reset. When it works it stops exactly at 12.

Last time I had to struggle a lot (Let the watch run for many hours or the chrono, adjust the watch via the crown/stem and then again try to reset.)

I have tried this without being too rough. I have not changed the dates when the time had been between 9-3, I have not reset the chrono when running it.

My questions:

1. Why is this happening? Is something broken? Or is it not lubricated?

2. Is it common? Is common on swiss movements or is only A7550?

2. Can it get worse? Is it dangerous to retry when it fails?

Right now I don't dare to touch the chrono anymore. At least I have a decent watch to tell me the time, but it is annoying that the chrono is not working properly.

When reading around in RWG I can see that some think the quality is poor on A7750 movements, but others claim the quality is very good. Right now I at least can not recommend

A7750.

Regards Mikael

[hooky]

I have bought an IWC 3717 with an A7750 movement. The watch works OK since a week (+1-2 min/day though).

I have tried the chrono and it works OK, starting and stopping. But at some occasions the reset does not work. The first time it happened after 10 tries, then it happen a week later.

Either it does not reset at all, sometimes it resets half the back to twelve, and sometimes it stops anywhere else (ie passes 12 and stops at eight o'clock,..). The subdials also fails to reset. When it works it stops exactly at 12.

Last time I had to struggle a lot (Let the watch run for many hours or the chrono, adjust the watch via the crown/stem and then again try to reset.)

I have tried this without being too rough. I have not changed the dates when the time had been between 9-3, I have not reset the chrono when running it.

My questions:

1. Why is this happening? Is something broken? Or is it not lubricated?

2. Is it common? Is common on swiss movements or is only A7550?

2. Can it get worse? Is it dangerous to retry when it fails?

Right now I don't dare to touch the chrono anymore. At least I have a decent watch to tell me the time, but it is annoying that the chrono is not working properly.

When reading around in RWG I can see that some think the quality is poor on A7750 movements, but others claim the quality is very good. Right now I at least can not recommend

A7750.

Regards Mikael

Hi Mikael,

don't know how technical you are with the watch already, since you are also a new member. You could try to open the case back and see if the Chrono device on top of the movement is functioning correctly. Maybe by that you could give this forums members more info to help you.

The chrono seconds could be slipping. That could be easily fixed by a watch smith i guess. Otherwise you could consider sending the watch back to the dealer for repair.

[anton]

Sounds like you have a problem with the chrono lever. Like the above poster, posting pictures would help. I can usually diagnose the problem from there.

As for the slipping of the chrono seconds hand, if that is related to the problematic reset, then you need to have the levers checked out.

If the chrono seconds hand slips after resetting the chrono, it means that your chrono hand is not inserted completely into the stem. Thus, the torque caused by the reset makes the hand "slip".

[Usil]

The word is that you just look at the chronos and not actually use them. Sensitive and prone to failure in the reps. Happens a lot. Sorry you did not read more posts on this.

Usil

[Watchmeister]

If your chrono hand is arbitrarily resetting I would guess it is simply hand slippage on the relevant post. If the hand is fully on check for slippage. SOP is often to glue it onto the post. By the way although it is certainly more common on Asian 7750's Swiss can have the same problem.

[RWG Technical]

The subdials also fails to reset. When it works it stops exactly at 12.

My questions:

1. Why is this happening? Is something broken? Or is it not lubricated?

2. Is it common? Is common on swiss movements or is only A7550?

2. Can it get worse? Is it dangerous to retry when it fails?

Based on the above statement, if the subdials and the center seconds hand both fail to reset to 12, the problem is with the reset hammer, there is one hammer for both the center seconds and the 30 minute subdial. If the hammer isn't moving all the way where it should to reset both gears, this is what you will see.

Why is it happening, don't know, only way to know is to look at the movement, something could be loose, something could be bent, there could be many reasons for this problem.

Not common at all, I have only seen this problem I think once in 3 years of fixing A7750's.

It can't get worse, but depending on what the problem is, something could be damaged. If your going to want to use the chrono, it would be a good idea to have it looked at, or return it to the dealer.

RG

[Watchmeister]

So much for my genius suggestions.

[RWG Technical]

So much for my genius suggestions.

The hands slipping are all too common, so your analysis is 99% of the time correct, it's unusual to have the hammer not work properly (if that is the problem).

I could be way off base, will have to wait for feedback to know exactly what is going on.

RG

[hooky]

Yes, Mikael, post us some pictures of the movement in running chrono position and when you have the resetpusher (almost) pushed in.

Then we might conclude better...

[Mike1718]

Yes, Mikael, post us some pictures of the movement in running chrono position and when you have the resetpusher (almost) pushed in.

Then we might conclude better...

OK I'll take some pictures. Do you want me to open upp the back?

Are there parts that should be visible? I'm thinking of the rotor

/Mikael

[hooky]

I am no expert here, but if you need to give more feedback. Could be simple, but also more difficult problem.

For pictures, you should open the caseback, maybe best to remove the rotor as well, to have a better view. Careful there.

Picture of when the movement is in the chrono stop setting, before resetting. Can the lever of the reset button touch the other lever while in 'stop' setting? Maybe you can take a pic of that. That is my best guess, to give feedback to the other experts to this forum.

Cheers and good luck,

J.

[Mike1718]

I tried to photo when resetting and when the back was removed.

Now it seems that the chrono is broken :-(.

The reason why: See the attached photo. This arm fell out of the watch. Now the start and stop button seems not to work.

The reset button seems to work fine. I'm not able to take a photo of this part in the movement when resetting but it looks OK - an arm is clearly moving.

But as I said before the start/stop button does not engage/work anymore. I assume the loose arm has someting to do with the chrono.

[RWG Technical]

Based on the above statement, if the subdials and the center seconds hand both fail to reset to 12, the problem is with the reset hammer, there is one hammer for both the center seconds and the 30 minute subdial. If the hammer isn't moving all the way where it should to reset both gears, this is what you will see.

As I said in the above, your problem is with the reset hammer...

That piece in your picture, is the Reset Hammer, it's broken in two pieces and there is a rivet somewhere in the case (or maybe still attached to the hammer arm), your best option at this point is to NOT wind the watch, and return it to the dealer and get a new one. Or send it to a watchsmith to repair and replace the hammer.

RG